The present invention relates to a synchronized reproduction system and a synchronized reproduction method in which an image reproduction device and a sound reproduction device reproduce multimedia data including image data and sound data in synchronization.
A reproduction device transmits and receives a stream including image data and sound data via a network to reproduce a video image including sound. For example, such a synchronization reproduction technology is implemented using the Real-time Transport Protocol (RTP) specified by the RFC 1889.
However, when an image reproduction device and a sound reproduction device are separated, such as a set-top box connected to a projector which projects an image and an amplifier connected to a speaker which outputs sound, synchronization cannot be achieved using the RTP.
Therefore, technology has been proposed in which each reproduction device achieves synchronization using the RTP Control Protocol (RTCP) and the Network Time Protocol (NTP) while adjusting the reproduction time based on a reference clock signal.
However, since the RTCP requires about 5% of the transmission bandwidth for command transmission and reception, the band for transmitting the contents is reduced.
Technology has also been proposed in which a specific synchronization signal is added to a stream. However, this technology further reduces the transmission band and requires a process of adding the synchronization signal to the stream, whereby the device configuration becomes complicated.
For example, JP-A-2006-148679 discloses a data processing device which receives a data stream, reproduces the data stream, and reproduces an image and sound in synchronization using time information of image data and time information of sound data included in the data stream.
However, the method disclosed in JP-A-2006-148679 requires a process of reproducing the data stream and a storage area for storing the reproduced data stream.